The Y-chromosomal short tandem repeat (STR) locus DYS385 can be typed using PCR amplification and separation of the resulting polymorphic fragments by non-denaturing high resolution polyacrylamide gel electrophoresis followed by silver staining. The PCR primers amplify a duplicated repeat sequence on the Y chromosome revealing a two-band pattern in male individuals. To determine the internal repeat structure as a basis for a consensus nomenclature, DNA sequence analysis was carried out after subcloning of PCR-amplified fragments revealing the uniform 4-bp repeat structure 'GAAA'. The shortest allele observed consisted of 10 repeat units thus providing the basis for the designation 'allele 10'. Except for isolated point mutations, no systematic differences could be observed either in the repeat sequence or in the flanking regions between the two fragments of a given individual. Thus it was not possible to discriminate between the two loci of the DYS385 system. Four population samples of German (n = 146), Chinese (n = 100), Japanese (n = 100), and Thai (n = 95) origin were studied. In the four groups, alleles 10 to 24 could be observed and genotype frequencies differed significantly. In Germans only one common genotype was present (11-14; 33.8% frequency). In the Asian populations, the frequencies were more evenly distributed with the 13-13 genotype (9%) in Chinese, the 13-17 genotype (14%) in Japanese and the 14-18 genotype (7%) in Thai being the most common. Overall, 69 different genotypes were found, of these 36 were observed in Germans, 36 in Chinese, 33 in Japanese and 44 in Thai. No mutations were detected in 62 father-son pairs. Thus DYS385 is a highly polymorphic STR system with population-specific genotype distributions.